1. Field of the Invention
The present invention relates to a method of manufacturing polymer films having second order non-linear optical properties such as second harmonic generating (SHG), the Pockels effect, or the like, and to polymer films and a non-linear optical element.
2. Description of the Related Art
In recent years, non-linear optical materials have been applied to optical devices such as ultra fast optical switches, phase compensator, wavelength converter, and the like. Spin coating has conventionally been used as a method for manufacturing a polymer film used as a non-linear optical material.
In a conventional spin coating method, a polymer solution is applied dropwise onto a rotating substrate, which is thereafter rotated at high speed. Thus, centrifugal force works uniformly on the polymer solution such that regions exhibiting the function of second order non-linear optical properties (hereinafter, such regions are referred to as xe2x80x9cchromophoresxe2x80x9d) cannot be orientated. As a result, in order to express second order non-linear optical properties in a polymer material, a process (poling) is required in which an external electric field is applied at a temperature higher than or equal to the glass transition temperature (Tg) so as to orientate the dipoles.
However, the conditions of the poling may lead to an alteration of the polymer substance. Further, even at temperatures less than or equal to Tg, it is easy for the dipoles which have been orientated by the poling to become disorientated Thus, the phenomenon of orientational decay is unavoidable after electric field poling.
An object of the present invention is to provide a method of manufacturing a polymer film having second order non-linear optical properties, such as second harmonic generating (SHG) or the Pockels effect or the like, which polymer film has excellent stability of the orientated molecules and whose orientated molecules do not become disorientated, and to polymer films, and a non-linear optical element.
The above-described objects are achieved by the following means.
The first aspect of the present invention is a method of manufacturing a polymer film having second order non-linear optical properties, the method comprising the steps of: placing a polymer solution between two substrates which are disposed substantially perpendicular with respect to a rotating stand and substantially symmetrical with respect to a rotation axis of the rotating stand; and rotating the rotating stand to form a polymer film having second order non-linear optical properties due to centrifugal force arising at the polymer solution.
In the second aspect of the present invention, in the method of the first aspect, the polymer solution is a solution in which at least one of the following types of polymers is dissolved in an organic solvent: (1) a host-guest polymer in which low molecular weight compounds are dispersed in polymers; (2) a modified polymer in which regions which express a function of second order non-linear optical properties are chemically modified in polymer side chains and/or a polymer main-chain; and (3) a crosslinked polymer.
In the third aspect of the present invention, in the method of the first aspect, the polymer solution is a solution in which a modified polymer, in which regions which express a function of second order non-linear optical properties are chemically modified in polymer side chains and/or a polymer main chain, is dissolved in an organic solvent.
In the fourth aspect of the present invention, in the method of the first aspect, the step of placing the polymer solution between the two substrates includes injecting the solution.
In the fifth aspect of the present invention, in the method of the first aspect, the step of rotating the rotating stand includes rotating the stand at a rotational speed of 1000 to 5000 rpm.
In the sixth aspect of the present invention, in the method of the fifth aspect, the rotating stand is rotated at a rotational speed of 2000 to 3000 rpm.
In the seventh aspect of the present invention, in the method of the first aspect, the two substrates are separated by a gap of 0.3 to 2 mm from one another.
In the eighth aspect of the present invention, in the method of the seventh aspect, the gap is from 0.5 to 1.5 mm.
In the ninth aspect of the present invention, in the method of the third aspect, the step of placing the polymer solution between the two substrates includes injecting the solution.
In the tenth aspect of the present invention, in the method of the third aspect, the step of rotating the rotating stand includes rotating the stand at a rotational speed of 1000 to 5000 rpm.
In the eleventh aspect of the present invention, in the method of the third aspect, the two substrates are separated by a gap of 0.3 to 2 mm from one another.
In the twelfth aspect of the present invention, in the method of the ninth aspect, the two substrates are separated from one another by a gap of 0.3 to 2 mm, and the step of rotating the rotating stand includes rotating the stand at a rotational speed of 1000 to 5000 rpm.
In the thirteenth aspect of the present invention, in the method of the twelfth aspect, the rotating stand is rotated at a rotational speed of 2000 to 3000 rpm, and the gap is from 0.5 to 1.5 mm.
The fourteenth aspect of the present invention is a polymer film having second order non-linear optical properties, the polymer film being manufactured by a method including the steps of: placing a polymer solution between two substrates which are disposed substantially perpendicular with respect to a rotating stand and substantially symmetrical with respect to a rotation axis of the rotating stand; and rotating the rotating stand to form a polymer film having second order non-linear optical properties due to centrifugal force arising at the polymer solution.
In the fifteenth aspect of the present invention, in the polymer film of the fourteenth aspect, the polymer solution is a solution in which at least one of the following types of polymers is dissolved in an organic solvent: (1) a host-guest polymer in which low molecular weight compound are dispersed in polymers; (2) a modified polymer in which regions which express a function of second order non-linear optical properties are chemically modified in polymer side chains and/or a polymer main chain; and (3) a crosslinked polymer.
In the sixteenth aspect of the present invention, in the polymer film of the fourteenth aspect, the polymer solution is a solution in which a modified polymer, in which regions which express a function of second order non-linear optical properties are chemically modified in polymer side chains and/or a polymer main chain, is dissolved in an organic solvent.
The seventeenth aspect of the present invention is a non-linear optical element comprising a polymer film having second order non-linear optical properties, the polymer film being manufactured by a method including the steps of: placing a polymer solution between two substrates which are disposed substantially perpendicular with respect to a rotating stand and substantially symmetrical with respect to a rotation axis of the rotating stand; and rotating the rotating stand to form a polymer film having second order non-linear optical properties due to centrifugal force arising at the polymer solution.
In the eighteenth aspect of the present invention, in the non-linear optical element of the seventeenth aspect, the polymer solution is a solution in which at least one of the following types of polymers is dissolved in an organic solvent: (1) a host-guest polymer in which low molecular weight compounds are dispersed in polymers; (2) a modified polymer in which regions which express a function of second order non-linear optical properties are chemically modified in polymer side chains and/or a polymer main chain; and (3) a crosslinked polymer.
In the nineteenth aspect of the present invention, in the non-linear optical element of the seventeenth aspect, the polymer solution is a solution in which a modified polymer, in which regions which express a function of second order non-linear optical properties are chemically modified in polymer side chains and/or a polymer main chain, is dissolved in an organic solvent.
When a polymer solution is placed between two substrates, which are disposed perpendicularly with respect to a rotating stand and symmetrical with respect to the rotation axis of the rotating stand, and the rotating stand is rotated, the orientation of the molecules of the polymer film is in-plane orientated due to the centrifugal force arising at the polymer solution, and is parallel to the direction of flow, such that the orientations are opposite at both ends of the substrate. Accordingly, a polymer film exhibiting two polar orientations within the same plane is formed.